title: Osteopontin: a uranium phosphorylated binding-site characterization.
abstract: Herein, we describe the structural investigation of one possible uranyl binding site inside a nonstructured protein. This approach couples spectroscopy, thermodynamics, and theoretical calculations (DFT) and studies the interaction of uranyl ions with a phosphopeptide, thus mimicking a possible osteopontin (OPN) hydroxyapatite growth-inhibition site. Although thermodynamical aspects were investigated by using time-resolved laser fluorescence spectroscopy (TRLFS) and isothermal titration calorimetry (ITC), structural characterization was performed by extended X-ray absorption fine structure (EXAFS) at the U LIII -edge combined with attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy. From the vibrational and fluorescence spectra, several structural models of a UO2 (2+) /peptide complex were developed and subsequently refined by using theoretical calculations to fit the experimental EXAFS obtained. The structural effect of the pH value was also considered under acidic to moderately acidic conditions (pH 1.5-5.5). Most importantly, the uranyl/peptide coordination environment was similar to that of the native protein.
authors.affiliation: Groupe Radiochimie, Institut de Physique Nucléaire d'Orsay, Université Paris XI Orsay, 15 Rue Georges Clemenceau, 91405 Orsay, France.
authors.forename: Samir
authors.initials: S
authors.lastname: Safi
authors.forename: Gaëlle
authors.initials: G
authors.lastname: Creff
authors.forename: Aurélie
authors.initials: A
authors.lastname: Jeanson
authors.forename: Lei
authors.initials: L
authors.lastname: Qi
authors.forename: Christian
authors.initials: C
authors.lastname: Basset
authors.forename: Jérome
authors.initials: J
authors.lastname: Roques
authors.forename: Pier Lorenzo
authors.initials: PL
authors.lastname: Solari
authors.forename: Eric
authors.initials: E
authors.lastname: Simoni
authors.forename: Claude
authors.initials: C
authors.lastname: Vidaud
authors.forename: Christophe
authors.initials: C
authors.lastname: Den Auwer
mesh_terms: D017886:Durapatite / Q000737:chemistry; D007477:Ions / Q000737:chemistry; D008958:Models, Molecular; D053495:Osteopontin / Q000737:chemistry* / Q000378:metabolism; D010748:Phosphopeptides / Q000737:chemistry; D010766:Phosphorylation; D011485:Protein Binding; D017550:Spectroscopy, Fourier Transform Infrared; D013816:Thermodynamics; D014501:Uranium / Q000737:chemistry* / Q000378:metabolism
chemical_list: D007477:Ions; D010748:Phosphopeptides; D053495:Osteopontin; D014501:Uranium; D017886:Durapatite
keywords: EXAFS spectroscopy; actinides; density functional calculations; protein structure; uranium